Nu-alkylidene, nu-cycloalkylidene, and nu-aralkylidene aliphatic diamines



.at'ented Feb. 18, 1947 I N -ALKYLIDENE, N-CYCLOALKYLIDENE, AND

N-ARALKYLIDENE ALIPHATIC DIAMINES Richard E. Brooks, Edgemoor Terrace, Del, as-

signor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application December 7, 1944,

Serial No. 567,131

9 Claims. (Cl. 260-566) This invention relates to the preparation of nitrogen compounds and more particularly to improvements in. the preparation ,of certain polyamide intermedates, namely, N-monoalkylidene' diamines, N,N'-dialkylidene' diamines, N-monoaralkylidene diamines and N,N'-diaralkylidene diamines, which substances are readily converted to N-monoalkyl diamines, N,N-dialkyl diamines, N-monoaralkyl diamines, and N,N'-diaralkyl diamines.

It is already known that N,N'-dialkylidene diamines may be prepared by condensation of carbonyl compounds with aliphatic diamines (Ben, 20, 267). In general the heretofore available methods of preparing N,N-dialkylidene diamines have been somewhat unsatisfactory in that appreciable .amounts of polymeric materials have been produced as by-products. Moreover, it has been especially difilcult to prepare the N-monoalkylidene diamines. If a solvent is employed to decrease the rate of formation of polymeric byproducts, the reaction between the carbonyl compound and the aliphatic diamine generally does not take place completely, and the yields of N- mono-alkylidene diamine and N,N'-dialkylidene diamine are accordingly somewhat low. A brief review of methods for preparing such aldehydeamine condensation products appears in J. A. C. S. 66,182 (1944). In accordance with the prior art, N-alkylidene aliphatic amines have been hydrogenated to yield N-alkyl amines.

An object of this invention is to prepare all-- Dhatlc N-monoalkylidene dlamines, N,N-diall=rylidene diamines, N-monoaralkylidenediamines and N,N-diaralkylidene diamines in high yields and in the absence of appreciable quantities of polymeric by-products. Another object is to provide a process for the manufacture of products which, on hydrogenation, yield N-monoalkyl, N,N-dialkyl, N-monoaralkyl, and N,N-diaralkyl diamines. Other objects will appear hereinafter.

These objects are accomplished in accordance with the invention by treating an aliphatic diamine with a carbonyl compound of the class water is not completely soluble. In the latter method the water layer may be separated from the reacting mixture by decantation.

Any aliphatic diamine may be employed in the practice of this invention. Suitabl aliphatic diam nes are members of the homologous series, H2N(CH2)nNH2, n being an integer, examples of which are ethylene diamine, trimethylenediamine, 1,3-diaminobutane, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, decamethylenediamine, and the like. Suitable carbonyl compounds of the class consisting of aldehydes and ketones are formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, lsobutyraldehyde, acetone, ethyl methyl ketone, cyclehexanone, benzaldehyde, and the like. If desired, the initial molar ratio of carbonyl compound to diamine may be from about 10:1 to about 1:10, preferably about 1:1 to about 2:1. Suitable water-removing agents are isopropanol, isobutanol, hexane, octane, benzene, toluene, cyclohexane, methylcyclohexane and the like. The preferred water-removing agents or carriers are substances which dissolve lioth the aliphatic diamine and the carbonyl compound, and which also are stable towards hydrogen under the conditions employed in a, subsequent hydrogenation of the N-monoalkylidene, N,N-dialkylidene, N-

monoaralkylidene and N,N'-diaraikylidene aliphatic diamines produced. Cyclohexanc is a substance which is particularly well suited for these purposes.

The preparation of aliphatic N-monoalkylidene, N,N'-dialkylidene, N-monoaralkylidene and N,N'- diaralkylidene diamines isgenerally conducted in accordance with the invention by adding an aliphatic or aromatic aldehyde or ketone or cycloaliphatic ketone to an aliphatic diamine in a solvent, maintaining the resulting mixture at a temperature preferably within the range of about 20 to about C., and removing the water thus produced by azeotropic distillation or decantation. During the early stages of the reaction it is desirable to cool'the mixture, keeping the temperature below about 55 C. The reaction takes place fairly rapidly and, if the solvent is water-insoluble,water separates as a layer soon after the reactants are mixed. This layer may be removed either by distillation or decantation, but is preferable to removethe water by azeotropic distillation, since the water layer frequently contains dissolved reactants. In one embodiment, after the water thus formed has been removed, distillation of the solvent is begun, and during this time, reaction continues to take place a-naoss as shown by the formation of additional amounts of water. In-order to force the reaction to completion the reaction mixture is heated and distillation is continued until formation of water virtually ceases. If, in one mode of practicing the invention, it is desired to isolate the N-alkylidene aliphatic diamines, the solvent may be removed by distillation, and the resulting residue may be distilled, preferably at diminished pressures. In this way N-alkyl'idene aliphatic diamine are produced in yields of as high as about 86%.

If it is desired to prepare N-alkyl or N-aralkyl aliphatic diamines without isolation of the N-alkylidene and N-araikylidene aliphatic diamines,

the solution oi aliphatic diamine-carbonyl com- 15 pound condensation product obtained after dis-- tillation of water from the aliphatic diamine-carbonyl compound reaction mixture is hydrogenated directly, generally at superatmospheric pressure (preferably about 20 to 1000 atmospheres) at a temperature of about to 250 in the presence of a hydrogenation catalyst. This procedure has advantages over hydrogenation of mixtures of carbonyl-compound and diamine, for such mixtures give rise to the formation or large amounts of water during the hydrogenation. Suitable hydrogenation catalysts for the hydrogenation of the solutions of aliphatic diamine-carbonyl compound condensation products in accordance with this inventlon include those elements of the 1st, 2nd, 6th, 7th, and 8th groups of the periodic system which have a hydrogenation action, and compounds or alloys of those elements, in particular copper, palladium, platinum. iron, cobalt and nickel. either alone or in conjunction with each other. Particularly eflective as catalysts for this purpose are nickel alloy catalysts, finely divided nickel supported on kieselguhr, finely divided cobalt and the like. In certain instances small amounts of alkali (about 0.1 to 2.0%) in these catalysts according to the invention have a beneficial eiIect on the hydrogenation reaction. In general hydrogenation catalyst supports and/or promoters, such as aluminum, thorium, silicon, and chromium oxides, pumice, silica gel, and kieselguhr may be 45 used in conjunction with these catalysts,

- The invention is further illustrated by means of 1 the following examples:

Example 1.To 58.1 grams (0.50 mole) hexa- B. P. 75 to 82 C.; 8.1 grams foreshots, B. P. 08

g idenehexamethylenediamine from three diflerent preparations was 1.4465, 1.4467, 1.4469 at 25 C. (D line).

Example 2.To 116.2 grams (1.00 mole) hexamethylenediamine, H2N(CH2)sNH:, dissolved in 765.4 grams (1000 milliliters) cyclohexane was 1 added 108.9 grams (1.51 moles) isobutyraldehyde,

(CH3) sCHCHO, dropwise with stirring over 2.0 hours maintaining the temperature at about 38 C. The reaction was allowed to continue for 1.3 hours at this temperature, then overnight at room temperature. The resulting mixture was sens-r rated into 932.2 grams or clear, water-white upper layer and 50.2 grams of cloudy, faintly yellow, slightly viscous lower layer. An aliquot composited of upper and lower layers was freed of water by azeotropic distillation, then hydrogenated- (see Example 6). Isolation of N-monoisobutylhexamethylenediamine and NJW-diisobutylhexamethylenediamine indicated 1.7% conversion to recovered hexamethylenediamine, 43.0% conversion to N-monoisobutylidenehexamethylenediamine, HaN(CHa)cN=CI-ICH(CH3)2, 42.3% conversion to N,N'-diisobutylidenehexamethylenedlamine, (CH3) 2CHCH=N(CH2) sN=CHCH(CH5) and 6.1% conversion to higher boiling materials (not distilled).

Example 3.-To 88.1 grams (1.00 mole). tetra.- methylenediamine, mmcmmm. dissolved in 379.6 grams (500 milliliters) cyclohexaue was added 144.2 grams (2.00 moles) isobutyraldehyde, (CHshCI-ICHO, dropwise with stirring over 2.5 hours, maintaining the temperature at 40 to C. After processing an additional 2.5 hours under these conditions and overnight at room temperature, 35.0 grams or water produced by the reaction was removed by azeotropic distillation. Distillation or 254.7 grams of the 602.0 grams of pale orange, slightly cloudy, residual reaction product gave: 149.2 grams recovered cyclohexane,

to 116 C'./20 mm. (8.3% conversion); 84.8 grams N.N'-diisobutylidenetetramethylenediamine,

- sion=88.4%) 11.0 grams higher boiling, dark brown oily liquid, not distilled (11.2% conversion) Analytical data obtained on the N,N-diisobutylmethylenediamme" H3N(CH2)UNH,; dissolved in idenetetramethylenediamine out were: neutral 650 milliliters of cyclohexane, was added 72.1 grams (1.00 mole) isobutyraldehyde,

(CH3) :CHCHO equivalent=99.1 and 99.0 (theory=98.l0),

N=14.1% (theory="l4.28%), refractive index== 1.4473 at 25 C. (D line).

Example 4.--To 61.4 grams (1.00 mole) ethy dropwise with stirring during a period of 0.5 hour. so enediamine, 98% HzNCI-lzCHzNfi'a. i s lv d in maintaining the temperature at to 452 C. The reaction mixture was processed an additional 0.5 hour under these conditions, after which'the waterformed was separated Iromthe organic layer.

- (2.00 moles) isobutyraldehyde,

379.6 grams cyclohexane was added 144.2 grams (CHahCHCHO. dropwise with stirring over 8.8 hours, maintaining the temperature at 42 to 48 C. After standing The product was then distilled, and further so overnight the product was filtered by suction.

amounts of water were collected as cyclohexane water binary. The remaining cyclohexane solvent was thereafter removed by distillation, following which there was obtained: 2.3 grams fore- The nearly water-white filtrate, which formed two layers, was distilled.- In addition to recovered cyclohexane solvent, there was obtained: about 34.0 grams foreshots (evidently crude N-inonoshots, B. P. 121 to 126 C./7 to 6 mm. (2.1% isobutylldeneethylenediamine) B. P. 52,5 mm.

conversion); 94.5 grams N,N'-diisobutylidenehexamethylenediamlne,

(0H3) 2CHCH=N(CH2) su=cncmcno 2 t 45/2 mm. (about 29.8% conversion); about 82.5 grams N,N'-diisobutylideneethylenediamine, B. P. 45 to 48 C./2 mm. (about 49.1% conversion) about 22.0 grams high boilers, 47 to 158/2 B. P. 128 to 133C./7 to 8 mm. (84.4% conmm. including 9.1 grams undistilled brown, viaversion) 9.9 grams higher boiling, medium brown oily liquid, not distilled (8.8% conversion). The neutral equivalent of the N,N'-diisobuty1idenehexamethylenediamine cut was 112.6 (theory= cous oil (about 13.1% conversion). equivalent of the N.N'-diisobutylideneethylenedi- 1 amine cut was 86.3 (theory=84.08).

Example 5.40.0 grams (0.178 mole) N,N'-di- 112.11). 'Ifhe refractive index of N.N-diisobutylisobutylidenehexamethylenediamine, 200 milli- B.-P.-116to 119 0/20 to 19 mm. (converf The neutral liters cyclohexane 101/2 mm. to 111/-2.5 mm.

' Distillation of the A I Aaazaoae an 1.0 gram platinum oxide (PtOz) was shaken in a. silver-lined tube for 2 hours at 7 to 33 C. under 525 to 725 atmospheres hydrogen pressure. A pressure drop of 105 atmospheres occurred. The 178.9 grams of product was filtered and the tube and filter residue were washed with methanol. Distillation of the water- .8 grams recovered meth- 3.3 gram ioreshots, B. P. 91 to 98 C./3 to 1.5 mm. (8.1% conversion): 35.1 gram N,N'-diisobutylhexamethylenediamine,

(CH3)2CHCH2NH(CH:)oNHCI-I2CH(CH:02, B. P. I

(86.1% conversion);

0.9 gram distillation residue, clear oil (2.2% conversion) Titration of the methanol-cyclohexane cuts indicated 0.1% conversion to volatile bases.- hexamethylenediamine cut was 114.4 and 113.9 (theory=114.11).-

. Example 6r-49-5 grams oian undistilledmiir- The neutral equivalent of the N,N 'v-diisobutyl- I ture of N-monoisobutylidenehexamethylenedidiamine in 169.9

methylenediamine in 1.5/11 mole ratio with azeotropic distillation to remove water) and 1.0 gram 1 platinum oxide catalyst were shaken in a. silver-' lined tube for 2 hours at sure drop of 155 atmospheres was observed. The 198.2 grams of productwas filtered and the tube and filter residue were washed with methanol. clear, pale yellow filtrate gave: 282.0 grams recovered methanol (0H3)zcncnmmcmnmrcmcmcmn' 3.8 grams undistilled brown oily liquid (6.1% conversion). Titration of the methanol-cyclohexane cuts indicated less than 0.2% conversion to volatile bases. Analyse of'theN-monoisobutylhexamethylenediamine out were: neutral equivalent= 86.5 (theory=86.10) and refractive index=1.4468

at 25 C; (D line) and oi the N,N'-diisobutylso hexamethylenediamin out were: neutral equivalent, 112.4 (theory=114.11); refractive index= 1.4437 at 25 C. (D line);

' amine and N,N' diisobutyiidenehexamethylenegrams cyclohexane (which had been preparedfrom isobutyraldehyde and hexa-s B. P195" to 101" 3 to 3010. under 545 to785 atmospheres hydrogen pressure.v A'presj incmcmcnoeomomcrroomomomcnooomen.

and cyclohexane; 0.5 gram recovered.hexaniethylenediamine, B. P.

11p to C./1.5 1 grams H2N(CH2) aNHCHaCH(CHa)2, B. P. 83 to 91 mm. (43.0% conversion); 24.1

B. P. 102 to 117/2 mm. (42.3% conversion):

Example 7.39.3 grams (0.20 mole) N,N' -di- 2.9 grams foreshots, B. P. 111 to '119/9 mm. (7.3% conversion); 34.3 grams" N,N' diisobutyltetrame'thylenediamine,

(CH3) QCHCHZNH(CH2) eNHCHzCHKJHa) a B. P. 119 to 120 C./10 to 7 mm. (85.8% 'conver- N,N'-diisobutyltetramethylenediamine out was 76 1.7 grams foreshots, B. P. 62

' conversion).

25C.),(Dline). 1

The foreshots from three hydrogenation runs,

' I refractive index, 1.5152

grams (0.177 mole) N,N-diisobutylideneethylenecyclohexane and 1.0 gram 6.1 grams recovered methanol and cyclohexane; (28% conversion) 53.9 grams product, 'B. P. 64 to 117/18 mm. and 61 to 42/1 to 0.5 mm. (88.5%

1 conversion) 0.7 gram undistilled brown oil (1.2%

separated the product into '(a) N.N'--d1isobutylethylenediamine, 1.- w j 1: (CH3) 2CHCH2NHCHaCHzNHCH2CH(CH3) a 0122 mnn, neutral equivalent= 25 C. (D line) m'opylimidazolidine,

1 a. rI'. 1ao-t6 1'31 c'./22 mm.,

114.6;(the0ry=113.12). Example 9.A

178 C. at a pressure of about 1 millimeter. This product was fair methylenediamine (neutral equivalent,

150.1; theory, 148.12; refractive index, 1.5413 at conducted as above were redistilled' at 25 (D'line). Example 10.-'-To a. mixture =1.4ass at 25 c. (in line);

to 63 c./1a mm. I

Redistillation of-the principal cut 86.3 (theory=86.10),'refractive index=1.4457 at and (b) 1.3-diisobuty1-3- i8oneutral equivalent; mixture containing 500 miniliters of cyclohexane and 92.6

methylenediamine was heated ly pure N,N'-dibenzylhexa- 149.4,

45 to 55 C. was added 72.1 grams (1 mole) of isobutyraldehyde with stirring over a period of 1.4 hours. The stirring was continued for 0.5 hour after which the mixture was filtered and the filtrate was distilled. A cyclohexane-water fraction was recovered following which the remainder of the distillation was conducted at diminished pressure. This yielded a fraction (17 c. c.) having a boiling point of 68 to 73 at 5 to 6 millimeters. This material crystallized upon cooling and was identified as hexamethylenediamine. The next fraction (51 c. c.) boiled largely at about 82 at a pressure of 7 millimeters. This fraction consisted principally of N-monoisobutylidenehexamethylenediamine. The largest fraction (83 c. c.) was N,N'-diisobutylidenehexamethylenediamine which had a boiling point of 118 C. at about 6 millimeters.

The N-alkyiidene and N-aralkylidene diamines prepared in accordance with this invention are of particular value in the manufacture of diamines which are useful in the manufacture of polyamide resins. For example, the N-monoisobutylhexamethylenediamine and the N,N'-diisobutylhexamethylenediamine, the N-monobenzylhexamethylenediamine and the N,N'-dibenzylhexamethylenediamine are especially valuable as intermediates in the formulation of elastic polyamides. In general the quality of polyamide resins depends in part upon the purity of the intermediates, and the products obtained in accordance with this invention are of a sufliciently high degree of purity that polyamides of high quality can be prepared therefrom.

It is to be understood that the invention is not limited to the specific embodiments described in the examples, but that other methods of applying the principle of the invention may be empioyed'without departing from the spirit and scope thereof. Accordingly, I do not limit myself except as set forth in the following claims.

The N-alkylidene diamines, N-cycloalkylidene diamines, and N-aralkyiidene diamines which are prepared by the method described in the above specification include both the monoand di-substituted products, 1. e. the term N-alkylidene diamine as used herein means N-monoalkylidene diamines and/ or N,N'-dialkylidene diamines, and the term N-aralkylidene diamine as used herein means N-monoaralkylidene diamines and/or N,N-diaralkylidene diamines.

Iclaim:

l. A process for the preparation of compounds of the class consisting of N-alkylidene, N-aralkyl- .idene, and N-cycloalkylidene aliphatic diamines which comprises adding a carbonyl compound of the class consisting of aliphatic aldehydes, aliphatic ketones, aromatic aidehydes, aromatic ketones, mixed aliphatic-aromatic ketones and cycloaliphatic ketones to a solution of aliphatic diamirie in a solvent which is also a water-withdrawing azeotropic agent, maintaining the temperature during the addition of the carbonyl compound and during the initial stages of the resulting reaction at about 20 to 55 C. by cooling the reaction mixture, continuing the reaction at a temperature below 120? C., distilling an azeotropic mixture of water and the said waterwithdrawing azeotropic agent from the resulting reaction mixture until the formation of water by the reaction between the carbonyl compound and the diamine virtually ceases, whereby a product containing a compound of the class consisting of N-alkylidene, N-aralkylidene, and N- cycloalkylidene aliphatic diamines is produced in the absence of a substantial quantity of' polymeric product, and thereafter separating the said compound from the said reaction product.

2. The process for the preparation of compounds of the class consisting of N-alkylldene, N-aralkylidene, and N-cycioalkylidene aliphatic diamines which comprises adding slowly,- with stirring, a carbonyl compound ofthe class consisting of aliphatic aldehydes, aliphatic ketones, aromatic aidehydes, aromatic ketones, mixed aliphatic-aromatic ketones and cycloaliphatic ketones to an aliphatic diamine at a temperature within the range of about 20 to 55 C. in the presence of a water-withdrawing azeotropic agent and thereafter distilling an azeotropic binary of water and the said azeotropic agent from the resulting reaction mixture, whereby a. product containing a compound of the class consisting of N-alkylidene, N-aralkylidene and N-cycioalkylidene aliphatic diamines is produced and thereafter separating the said compound from the said reaction product.

3. A process for the preparation of N-isobutyiidene diamines which comprises adding isobutyraldehyde to an aliphatic diamine at a temperature within the range of about 20 to 55 C. in the presence of a water-withdrawing azeotropic agent and thereafter distilling a binary of water and the said azeotropic agent from the resulting reaction mixture, whereby a as the chief reaction products substantial amounts of both N-monoisobutylidene aliphatic diamine and N,N-diisobutylidene aliphatic diamines is produced, and thereafter separating said diamines from the said reaction product.

4. A process for the preparation of N -isobutylidenediamines which comprises adding isobutyraldehyde slowly, with stirring, to a solution of hexamethyienediamine in a solvent which is also a water-withdrawing azeotropic agen while cooling the mixture to maintain the temperature within the range of about 20 to 55 C., and thereafter distilling a binary of water and the said azeotropic agent from the resulting reaction mixture, whereby a distillation residue containing N-isobutylidenehexamethylenediamines as the chief reaction products is obtained.

5. The process set forth in claim 4 in which the said water-withdrawing azeotropic agent is cyclohexane.

6. A process for the preparation of N-isobutylidenediamines which comprises adding isobutyraldehyde slowly, with stirring, to tetramethylenediamine at a temperature within the range of about 20 to C. in he presence of a waterwithdrawing azeotropic agent and thereafter dietilling a binary of water and the said azeotropic agent from the resulting mixture whereby a product containing a substantial amount of both N- monoisobutylidenetetramethylenediamine a n d N,N' diisobutylidenetetramethylenediamine is produced without the formation of any substantial amount of polymeric material, and thereafter separating the said N-monoisobutylidenetetramethylenediamine and N,N diisobutylidenetetramethylenediamine from the resulting product.

7. A process for the preparation of N-benzylidenediamines which comprises adding benzaldehyde to a solution of an aliphatic diamine in a water-withdrawing azeotropic agent at a temperature in the range of about 20 to 55 C. and thereafter distilling an azeotropic binary of water and the said azeotropic agent from the resulting reaction mixture, whereby a product conmixture containing dene aliphatic diamine is produced and thereafter separating the said N-monobenzylldene ailphatic diamine and N,N'-dibenzylidene aliphatic diamine from the said reaction product.

8. A process for the denediamines which comprises adding benzaidehyde to a solution oi hexamethylenediamine in a solvent which is also a water-withdrawing azeotropic agent, maintaining the temperature of the preparation oi N-benzyli resulting mixture during the initial stages of the ensuing reaction at about to 50 the reaction mixture, and thereafter distilling an azeotropic binary of water and the said amtropic agent from the resulting reaction mixture whereby a product containing a substantial amount of both 'N-monobenzylidenehexamethylenediamine and N,N'-dibenzylidenehexameth- C. by cooling ylenediamine is produced and thereafter sep- 20 arating the said N-monobenzylidenehexamethylenediamine and N,N'-dibenzy1idenehexameth-,

ylenedlaxnine from the resulting reaction product.

9. A process for the preparation or N-benzylidenediamines which comprises adding benzaldehyde to a solution of hexamethylenediamine in cyclohexane with stirring. and maintaining the 9 ,taining a substantial amount oi both N-monobenzylidene aliphatic diamine and N.N'-dibenzyli- 10 temperature or the resulting mixture at about 40' to C. during the ensuing reaction, thereaiter distilling an azeotropic binary of water and cyclohexane from the resulting mixture whereby a residue containing N-monobenzylidenehexameth-f I ylenediamines is obtained, said residue being characterized in that it gives upon hydrogenation a mixture of N-monobenzylhexamethylenedlamine and N,N'-dibenzylhexamethylenediamine. a

RICHARD E. BROOKS.

REFERENCES CITED The following references are of record in the file of this patent:

STATES PATENTS v Date Y Clarkson Nov. 5, 1940 

